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US 8,077,397 B2Granted
Zoom lens and image projection apparatus including the same
AssigneeCanon Kabushiki Kaisha
InventorKazuhiro Inoko
Life of this patent
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AssigneeCanon Kabushiki Kaisha
InventorKazuhiro Inoko
Estimating the term…
A zoom lens includes, in order from an enlargement conjugate side to a reduction conjugate side, a first lens unit of negative refractive power; a second lens unit of positive refractive power; a third lens unit of positive refractive power, the third lens unit having at least three lens elements; a middle lens unit including at least one lens unit; and a last lens unit of positive refractive power. All the lens units, except the first lens unit and the last lens unit, move during zooming. The zoom lens satisfies appropriate conditions.
A zoom lens comprising, in order from an enlargement conjugate side to a reduction conjugate side:
An image projection apparatus comprising:
A zoom lens comprising, in order from an enlargement conjugate side to a reduction conjugate side:
An image projection apparatus comprising:
Dependencies are inferred from the claim text.
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From the US filing history. Foreign family members aren’t listed.
The first group being negative: arranged -++++
Optical objectives specially designed for the purposes specified below: telecentric objectives or lens systems
The first group being negative: arranged -++-+
Optical elements, systems or apparatus
About 2 years 3 months of term left · ends 4 Feb 2029 (estimated)
1. Field of the Invention
The present invention relates to a zoom lens and an image projection apparatus including the zoom lens. For example, the present invention relates to a zoom lens having a long back focus, providing a high level of optical performance, and suitable for a projector producing a projected image.
2. Description of the Related Art
FIG. 1 illustrates a lens configuration at a wide-angle end of a zoom lens according to a first exemplary embodiment of the present invention.
FIG. 2A and FIG. 2B are aberration diagrams of the zoom lens according to the first exemplary embodiment.
FIG. 3 illustrates a lens configuration at a wide-angle end of a zoom lens according to a second exemplary embodiment of the present invention.
The present invention provides a zoom lens capable of effectively correcting various aberrations during zooming, offering excellent optical performance throughout the zoom range, and suitable for a projector. Zoom lenses according to exemplary embodiments of the present invention will now be described.
A zoom lens according to each exemplary embodiment of the present invention includes, in order from an enlargement conjugate side to a reduction conjugate side, a first lens unit of negative refractive power, a second lens unit of positive refractive power, a third lens unit of positive refractive power, a middle lens unit having at least one lens unit, and a last lens unit of positive refractive power. The first lens unit is closest to the enlargement conjugate side, while the last lens unit is closest to the reduction conjugate side. In other words, the zoom lens of each exemplary embodiment has practically no lens unit other than the first lens unit, second lens unit, third lens unit, middle lens unit, and last lens unit. The enlargement conjugate side may be referred to as front (front side) or screen side. The reduction conjugate side may be referred to as rear (rear side) or panel side (original image side, display device side, or liquid crystal panel side).
If the zoom lens includes five lens units (the first, second, third, fourth, and fifth lens units in order from the enlargement conjugate side), the middle lens unit corresponds to the fourth lens unit (having positive or negative refractive power). If the zoom lens includes six lens units (the first, second, third, fourth, fifth, and sixth lens units), the middle lens unit includes, in order from the enlargement conjugate side to the reduction conjugate side, the fourth lens unit of negative refractive power and the fifth lens unit of positive refractive power. Alternatively, when the zoom lens includes six lens units, both the fourth lens unit and the fifth lens unit may have positive refractive power.